1. Field of the Invention
This invention relates to a method for enhancing the performance of a fluid bed catalyst which has lost activity or fluidization quality due to contaminants or other physical or chemical change on the surface of the catalyst. More specifically, the invention relates to a method for abrading the catalyst surface while in use to remove a thin layer of the catalyst surface thereby exposing fresh catalyst. Additionally, the invention relates to a method for deagglomerating catalyst particles.
2. Description of the Art
In a fluid bed catalytic reactor, finely divided solid particles of catalyst are contacted with a typically vaporous reaction medium. The catalyst particles are lifted and agitated by a rising stream of process gas such that they appear suspended in the gas stream and may resemble a boiling liquid, hence the term "fluid bed".
The most well-known and one of the early applications of fluid bed reactor technology is catalytic cracking of oils to produce gasoline and other light hydrocarbons. Other uses include coking of residua; coke gasification; catalytic oxidation of benzene or butane to maleic anhydride; ammoxidation of propylene to acrylonitrile; and hydrogen chloride oxidation to chlorine.
The instant invention focuses on the catalysts used in fluid bed reactors. Through use and over time, some fluid bed catalysts lose activity as the surface of the catalyst is fouled by contaminants or by-products generated by the reaction or as the surface of the catalyst undergoes a physical or chemical transition to a less catalytic form. Additionally, as contaminants or a physical or chemical change occur on the surface of the catalyst, some catalysts become "sticky" and the small fluid bed particles begin to agglomerate into larger particles. The agglomerated particles result in a decrease of catalytic surface area, thereby affecting the overall performance of the fluid bed catalyst. Further, the agglomerated particles impede the natural circulation and fluidization of the catalyst bed.
Typically, the solution to the above problems is to replace all or part of catalyst in the fluid bed reactor. This is very costly in terms of the cost of catalyst but also in the cost of lost production which could result from shutting down the fluid bed reactor to accommodate a catalyst changeout.
An object of the invention described herein is a method designed to cure the problems brought upon by agglomeration, contamination or a physical or chemical change on the catalyst surface and to prolong catalyst life.